“The doctrine of the Trinity is the most immense of all the doctrines of religion. It is the foundation of theology.
Christianity, in the last analysis, is Trinitarianism. Take out of the New Testament the person of the Father, the Son, and the Holy Spirit, and there is no God left. Take out of the Christian consciousness the thoughts and affections that relate to the Father, the Son, and the Holy Spirit, and there is no Christian consciousness left.
The Trinity is the constitutive idea of the evangelical theology, and the formative idea of the evangelical experience. The immensity of the doctrine makes it of necessity a mystery; but a mystery which like night enfolds in its unfathomed depths the bright stars— points of light, compared with which there is no light so keen and so glittering.
Mysterious as it is, the Trinity of Divine Revelation is the doctrine that holds in it all the hope of man; for it holds within it the infinite pity of the Incarnation and the infinite mercy of the Redemption. And it shares its mysteriousness with the doctrine of the Divine Eternity.
It is difficult to say which is most baffling to human comprehension, the all-comprehending, simultaneous, successionless consciousness of the Infinite One, or his trinal personality. Yet no theist rejects the doctrine of the Divine Eternity because of its mystery. The two doctrines are antithetic and correlative. On one of the Northern rivers that flows through a narrow chasm whose depth no plummet has sounded, there stand two cliffs fronting each other, shooting their pinnacles into the blue ether, and sending their roots down to the foundations of the earth. They have named them Trinity and Eternity. So stand, antithetic and confronting, in the Christian scheme, the trinity and eternity of God.”
As quoted in:
-White, James R. (1998-11-01). Forgotten Trinity, The (p. 20-21). Baker Publishing Group. Kindle Edition.
-William G. T. Shedd, “Introductory Essay” in Philip Schaff, ed., The Nicene and Post-Nicene Fathers, Series I (Grand Rapids: Eerdmans, 1956), 10– 11.